The total fertility rate, sometimes also called the fertility rate, absolute/potential natality, period total fertility rate or total period fertility rate of a population is the average number of children that would be born to a woman over her lifetime if:
Fertility is the natural capability to produce offspring.
Distilled Demographics: The Birth Rate by Population Reference Bureau
She were to experience the exact current age-specific fertility rates through her lifetime, and
Videographic: Are Asian fertility rates declining? by The Economist